Polyol compositions for polyurethanes

ABSTRACT

A polyol composition for reacting with a polyisocyanate to form a polyurethane resin, comprises: (a) a triglyceride of a C 12  to C 25  hydroxy-substituted fatty acid or a C 12  to C 25  hydroxy-substituted fatty acid and glycerol, which can react together to produce a triglyceride; and (b) at least 0.1 mole per mole of triglyceride (a) or triglyceride capable of being formed from the fatty acid and the glycerol, of an oxide, hydroxide, or carbonate of a metal from Group IIA of the periodic table. A composition for reacting with a polyisocyanate to form a polyurethane resin, comprises the reaction products of: (a) a triglyceride of a C 12  to C 25  hydroxy-substituted fatty acid, a C 12 to C 25  hydroxy-substituted fatty acid and glycerol, which can react together to produce a triglyceride: and (b) at least 0.1 mole, per mole of triglyceride (a) or triglyceride capable of being formed from the fatty acid and the glycerol, of an oxide, hydroxide or carbonate of a metal from Group IIA of the periodic table.

FIELD OF THE INVENTION

This invention relates to a polyol composition intended to react with apolyisocyanate to form a polyurethane resin.

BACKGROUND OF THE INVENTION

Polyurethanes have a very wide range of applications in surfacecoatings, protective flooring products, adhesives, sealants and the liketo provide protective surfaces with high resistance to aggressivechemicals, physical damage and abrasion. They exhibit very good adhesionto most substrates and can provide long term protection againstcorrosion and erosion in the most severe of environments. They aregenerally made by reacting together the components of a two-componentcomposition, one of which includes a polyisocyanate while the otherincludes a component having two or more hydroxyl groups to react withthe polyisocyanate.

It is to be understood that by “a two-component composition” we mean acomposition comprising two essential components. Such a composition mayadditionally comprise one or more other optional components.

Although it is possible to manufacture single component coating systemscontaining available isocyanate groups, which cure by reaction withatmospheric moisture, such products have limited application becausethey are invariably solvent-containing, difficult to pigment andunsuitable for situations where a high-build of coating, e.g. 100microns or more, is required.

For the above reasons, compositions based upon two components, usuallypolyhydroxy materials and polyisocyanates are preferred. Coatingsdesigned on this basis may contain particulate mineral fillers, pigmentsand other additives or materials, can be applied as thick films in oneapplication and usually offer improved performance compared with thesingle component moisture curing products. Because of the vast range ofavailable polyhydroxy compounds (polyols), it is possible to produce awide range of physical properties in the cured products. Coatings may bedesigned to be very hard, soft and elastomeric, or any physicalcharacter between these.

A problem which arises in making polyurethanes is that thepolyisocyanates used react easily with water, for example that containedwithin the raw materials used, in surfaces to which the polyurethane isto be applied or as atmospheric moisture. As well as reducing the numberof isocyanate groups available to react with the polyol, the reactionwith water generates carbon dioxide, leading to foaming and incompletecross-linking. This is particularly damaging in the case of protectivefilms. Steps therefore have to be taken to exclude water from thecomponents, and if the polyurethane is to be applied to a wet surfacesuch as an underground pipe, or damp concrete floor, or in externalconditions where surfaces are damp or may encounter rain, unwantedisocyanate reaction will inevitably result.

The inevitability of the reaction between isocyanates and water meansthat all raw materials for inclusion in conventional compositions mustbe water-free, or must be dried before or during inclusion and that suchcompositions are totally unsuitable for use where water is present.

EP-A-0 145 269 discloses two-component compositions which are capable ofcuring in the presence of water to form polyurethane resins. Thecompositions comprise highly reactive polyols and solvent-basedpropolymers with less reactivity than monomeric diisocyanates such asmethylene di-p-phenylene isocyanate (MDI) to and toluene isocyanate(TDI). A large excess of water and calcium hydroxide is employed by thecompositions to act as a scavenger for carbon dioxide produced. Thepolyurethane resins formed have limited strength and there aredisadvantages, such as flammability and environmental and disposalproblems of volatile organic solvents, inherent in the use ofsolvent-containing materials.

SUMMARY AND OBJECTS OF THE INVENTION

The present invention aims to provide a polyol composition for use as acomponent of a two-component polyurethane composition which exhibitscomplete water tolerance, and will even cure under water without anyunwanted effects resulting from isocyanate/water reactions.

In the first aspect the present invention provides a polyol compositionfor reacting with a polyisocyanate isocyanate to form a polyurethane,comprising:

(a) a triglyceride of a saturated or unsaturated C₁₂ to C₂₅,hydroxy-substituted fatty acid or a C₁₂ to C₂₅ hydroxy-substituted fattyacid (or Group IIA metal salt thereof) and glycerol, which can reacttogether to produce a triglyceride, and

(b) at least 0.1 mole (and preferably up to 2.0 mole), per mole oftriglyceride (a) or triglyceride capable of being formed from the fattyacid and the glycerol, of an oxide, hydroxide or carbonate of a metalfrom Group IIA of the periodic table.

On heating the composition in the presence of water, which may be addedor contained as an impurity, the triglyceride is hydrolyzed by theoxide, hydroxide or carbonate thereby breaking the ester bonds toproduce free fatty acid and glycerine (glycerol). The fatty acid is thensaponified by the oxide, hydroxide or carbonate to produce fatty acidsalts of the metal and the oxide, hydroxide or carbonate also reactswith the glycerine to produce metal glycerates.

Accordingly in a second aspect the present invention provides acomposition for reacting with a polyisocyanate to form a polyurethane,comprising the reaction products of:

(a) a triglyceride of a saturated or unsaturated C₁₂ to C₂₅hydroxy-substituted fatty acid or a C₁₂ to C₂₅ hydroxy-substituted fattyacid (or Group HA metal salt thereof) and glycerol, which can reacttogether to produce a triglyceride; and

(b) at least 0.1 mole (and preferably up to 2.0 mole), per mole oftriglyceride (a) triglyceride capable of being formed from the fattyacid and the glycerol, of an oxide, hydroxide or carbonate of a metalfrom Group IIA of the periodic table,

i.e. fatty acid salts of the metal and glycerates of the metal (andoptionally free fatty acid and glycerol), or a like mixture of fattyacid salts of the metal and glycerates of the metal (and optionally freefatty acid and glycerol produced other than by reaction of reactants (a)and (b)).

The fatty acid is preferably an unsaturated fatty acid with one or morehydroxy groups present in the aliphatic chain.

According to a third aspect of the invention there is provided acomposition for forming a polyurethane resin and comprising acomposition according to the first or second aspect of the invention anda polyisocyanate.

It has been found that such compositions, according to the third aspectof the invention, will cure in the presence of water, even whensubmerged, to a high strength and will exhibit a firm bond when appliedto wet surfaces such as steel, cast-iron or concrete, with nodeleterious effect from the presence of water.

Thus by means of the present invention, there can be provided two-partpolyurethane compositions which are water tolerant, cure to a highstrength and do not require the use of water or organic solvents withintheir formulations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The triglyceride is preferably provided by castor oil, i.e.: thecomposition according to the first aspect of the invention preferablycomprises castor oil.

Castor oil has as its main component (about 80%) the triglyceride ofricinoleic acid. Each ricinoleic side chain has a hydroxy group on theninth carbon atom and for this reason castor oil has frequently beenused as a low cost polyol in polyurethane compositions, although ittends to introduce flexibility, which may not be desired. We have foundthat castor oil, when hydrolyzed by an oxide, hydroxide or carbonate ofa metal from group IIA of the Periodic Table, produces a mixture oflong-chain hydroxy-containing salts of the metal and the glycerate ofthe metal.

The castor oil may be “first pressing” material, pharmaceutical gradecommercial or second grade. The oil should preferably conform to BS6501967 but this is not essential.

The metal oxide, hydroxide or carbonate is preferably a hydroxide of analkaline earth metal such as calcium, strontium or barium. Basiccarbonates such as magnesium carbonate may also be used.

The preferred component (b) is calcium hydroxide. When reacted withcastor oil this produces calcium ricinoleate, a difunctional polyol, andcalcium glyceride, a tetrafunctional polyol. The reaction proceeds intwo stages: in the first stage the oil is hydrolyzed to ricinoleic acidand glycerol, these then react with the calcium hydroxide producingwater molecules as well as the calcium salts (calcium ricinoleate andcalcium glycerate). The calcium salts produced have been found toproduce polymers (i.e. polyurethane resins) with very useful propertieswhen further reacted by combination with polyisocyanates.

The content of the calcium salts may be controlled by varying thestarting amount of calcium hydroxide employed and stopping the reactionwhen a desired content of the calcium salts has been reached by addingsufficient calcium oxide to react with the water produced and any waterwhich may have been present in the initial components. To affordimproved water tolerance, further calcium hydroxide (over and above theat least 0.1 mole, per mole of triglyceride previously referred to) maythen be added and no further hydrolysis or reaction will occur providedsufficient calcium oxide is present to remove any water present in theadditional calcium hydroxide.

The following table illustrates the range of physical properties thatcan be achieved by way of measurements of flexural strengths measured onthe polymers formed by reacting the partially or fully reacted castoroil with the calculated stoichiometric amount of4,4-diphenylmethanediisocyanate (M.D.I.). The proportion of calciumhydroxide quoted is the percentage of the stoichiometric quantityrequired to react fully with the hydrolysis products from the castoroil. 100% corresponds to 2 moles of calcium hydroxide per mole oftriglyceride, i.e. the stoichiometric amount of calcium hydroxide toreact fully with the hydrolysis products from the castor oil.

Flexural strength Flexural modulus % calcium hydroxide (Newtons/mm.Sq.)(Newtons/mm.Sq.) 5 15 102 10 22 185 20 27 235 40 44 582 60 64 941 80 691176 100 73 1487

Further variations can be made by the inclusion of othernon-hydrolyzable polyols, which may be difunctional, trifunctional,tetrafunctional or greater, with respect to the hydroxyl content. Thesemay be chosen from the commercially available polyether polyols, derivedfrom propylene glycol, ethylene glycol, trimethylol propane orbisphenols, and they may include polyols derived from hydroxy-containingpolybutadienes, modified alkyd resins, oil soluble phenolic resins,epoxy resin/amine adducts, hydroxyl containing epoxy resins, sugars orlow molecular weight polyols such as butane diol, mono propylene glycol,ethylene glycol and glycerol.

If the compositions according to the first and second aspects of theinvention are made using a fatty acid and glycerol, then the fatty acidand glycerol may react directly with the oxide, hydroxide or carbonateof the Group IA metal without intermediate formation of triglyceride andhydrolysis thereof.

A practical composition according to the first aspect of the inventionand comprising castor oil or other triglyceride and glycerol maycomprise 0.1 to 0.5 mole of the oxide, hydroxide or carbonate per moleof the glycerol in conjunction with calcium salts of one or more of thefatty acids. Successful use of such a composition may require thepresence of a further polyol to reduce viscosity and control reactivity.

The polyol composition of the invention may include other conventionalmaterials depending on the intended use of the polyurethane. Forexample, when preparing a surface coating or sealant it may be desirableto include a particulate mineral filler such as talc, china clay,calcium carbonate, barium sulphate, silica or slate flour. Furtheradditives may be included to control the rheology of the composition,for example clays, fumed silica or hydrogenated castor oil. As pigments,titanium dioxide or iron or chromium oxides or other suitable colorantsmay be included.

Where a surface coating composition needs to be provided withanti-corrosive properties, suitable anti-corrosive pigments or fillersmay be included, for example micaceous iron oxides, zincphosphate/borate combinations, basic aluminium/zinc phosphate, modifiedbarium borate, modified barium metaborate, basic zinc molybdate,strontium phosphate hydrate, zinc silicophosphate hydrate, zincmolybdate phosphate, basic zinc phosphate hydrate or other materialsused to inhibit corrosion of metallic surfaces.

For the production of a polyurethane suitable for use as a flooringcomposition there may be added, during manufacture or just prior toapplication, suitable graded granular materials such as silica sand,crushed flint, crushed marble, crushed granite, polyvinyl chlorideflakes, wood flour, rubber crumb or other similar materials.

If it is desired to reduce the viscosity of the polyol composition, asolvent may be included provided it is free of hydroxyl groups or otherforms of active hydrogen. Suitable solvents include toluene, xylene,methylene chloride, methyl ethyl ketone, methyl isobutyl ketone,acetone, methyl pyrrohidone, aliphatic or aromatic hydrocarbons,cyclohexane and ethyl acetate.

Isocyanates with which the polyol compositions of the invention may bereacted may be of any conventional type, including aliphatic,cycloaliphatic and araliphatic isocyanates. Among the polyisocyanateswhich can be used are tolylene diisocyanate (TDI), diphenyl methanediisocyanate (MDI), xylylene diisocyanate, isophorone diisocyanate,hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, 2,2,4-or 2,4,4-dicyclohexylmethyl diisocyanates,3-isocyanatomethyl-3,5,5-trimethyl cyclohexyl isocyanate or any otherliquid polyisocyanate material, including prepolymer formed by thereaction of an excess of any polyisocyanate with a suitable polyhydroxycompound or other isocyanate-reactive compound, such as hydroxvlterminated polyesters, hydroxyl terminated poiybutadiene glycol, aminoalcohols, polyamines, higher polyhydric alcohols, water,polyesteramides, polyesters or any other suitable precursors.

The polyol composition is preferably reacted with slightly morepolyisocyanate than is required to react completely with the availablehydroxyl groups in the polyol composition. The stoichiometric excess ispreferably from 10 to 20% but may be higher.

The invention will now be illustrated further by means of the followingexamples. It will be understood that the calcium hydroxide used in theexamples contains water (about 2% by weight) as an impurity.

EXAMPLE 1

A flooring mortar was prepared from the following composition:

PART A Castor oil 31.6 wt parts Calcium hydroxide 1.7 wt parts Calciumoxide 2.7 wt parts PART B Isophorone diisocyanate 10.0 wt parts PART CDried silica sand 120.0 wt parts

Parts A and B are mixed together at ambient temperature and Part C ismixed with the resulting mixture to produce the mortar, which cures to apolyurethane resin having a flexural strength of 20 N/mm. Sq. and aflexural modulus of 1,800 N/mm.Sq.

EXAMPLE 2

A flexible sealing material was prepared from the following composition:

PART A Castor oil 45 wt parts Polybutadiene polyol M.wt. 2800 30 wtparts Calcium hydroxide 2.2 wt parts Calcium oxide 3.3 wt parts PART B2,4,4-trimethyl hexamethylene 11.0 wt parts diisocyanate

Parts A and B are mixed together at ambient temperature to produce amixture which cures to form a flexible polyurethane resin having aflexural strength of 25 N/mm.Sq. and an elongation at break of 120%.

EXAMPLE 3

A water-tolerant surface coating was prepared from the followingcomposition.

PART A Castor oil 32.0 wt parts Calcium hydroxide 8.0 wt parts Calciumoxide 5.0 wt parts PART B Diphenylmethane 20.0 wt parts diisocyanate(MDI)

Parts A and B are mixed together at ambient temperature to form amixture which cures to produce a polyurethane resin having a flexuralstrength of 45 N/mm.Sq. and a modulus of 1,500 N/mm.Sq.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A method of forming a resin composition forforming a polyurethane resin, comprising: preparing a polyol compositioncomprising: reacting together: (a) a triglyceride of a C₁₂ to C₂₅hydroxy-substituted fatty acid; and (b) calcium hydroxide to hydrolyzethe triglyceride to yield a fatty acid in free form and glycerol; andsaponifying the fatty acid to give a fatty acid salt, the calciumhydroxide being provided in an amount of at least 0.1 mole per mole ofthe triglyceride; and combining the polyol composition with apolyisocyanate to form the resin composition.
 2. The method according toclaim 1, wherein water produced by the saponifying is removed byreaction with calcium oxide.
 3. A composition for forming a polyurethaneresin comprising: a polyol composition and polyisocyanate, the polyolcomposition having been prepared by reacting together: (a) atriglyceride of a C₁₂ to C₂₅ hydroxy-substituted fatty acid: and (b)calcium hydroxide to hydrolyze the triglyceride to yield a fatty acid infree form and glycerol; and saponifying the fatty acid to give a fattyacid salt, the calcium hydroxide being provided in an amount of at least0.1 mole per mole of the triglyceride.
 4. The composition of claim 3,wherein the hydroxy-substituted fatty acid is an unsaturated fatty acid.5. The composition of claim 3, wherein the hydroxy-substituted fattyacid is ricinoleic acid.
 6. The composition of claim 5, wherein thetriglyceride of ricinoleic acid is provided by castor oil.
 7. Apolyurethane resin formed by reacting a polyol composition with apolyisocyanate, the polyol composition having been prepared by reactingtogether: (a) a triglyceride of a C₁₂ to C₂₅ hydroxy-substituted fattyacid; and (b) calcium hydroxide to hydrolyze the triglyceride to yield afatty acid in free form and glycerol; and saponifying the fatty acid togive a fatty acid salt, the calcium hydroxide being provided in anamount of at least 0.1 mole per mole of the triglyceride.
 8. Thepolyurethane resin according to claim 7, wherein water produced bysaponifying the fatty acid is removed by reaction with calcium oxide. 9.The polyurethane resin according to claim 7, wherein thehydroxy-substituted fatty acid is an unsaturated fatty acid.
 10. Apolyurethane resin according to claim 7, wherein the hydroxy-substitutedfatty acid is ricinoleic acid.
 11. A polyurethane resin according toclaim 7, wherein the triglyceride of ricinoleic acid is provided bycastor oil.
 12. The composition claim 3, wherein water produced bysaponifying the fatty acid is removed by reaction with calcium oxide.